1. Field of the Invention
The present invention generally relates to the storage of digital data, and more specifically to multimedia data, on a physical medium.
The present invention more specifically relates to the protection of digital data contained on such a medium against unauthorized reproductions or changes, especially by the creator of the concerned medium. “Creator of the medium” is used to designate the person who has, first, recorded the data on the physical medium. He is not necessarily the author of the content of the multimedia data, nor is he necessarily the medium manufacturer.
An example of application of the present invention relates to multimedia media intended to receive music files or images in digital form.
2. Discussion of the Related Art
It has already been provided to cipher or encrypt data recorded on a multimedia medium (for example, a CDROM, a digital floppy disk, etc.) so that these data can only be read by a reader having the ciphering key. However, unless the medium manufacturing and the data recording in the manufacturing premises is individualized to individualize the key according to the user, the same medium can be read by any reader having this key. An object precisely is to forbid the reading from the physical medium by an unauthorized reader.
An example of a system of protection against illicit copies of any digital medium is described in note “Content protection for recordable media specification”—“Introduction and common cryptographic elements”, published by 4C-entity, Rev 0.03, Jun. 28, 2000, which is incorporated herein by reference.
It has also be provided to equip a physical medium with multimedia data of an integrated circuit (microcircuit) provided with means of calculation and means of storage of a list of identification codes of readers allowed to read the data. This list is recorded at the same time as the data and the corresponding readers are then capable of deciphering the stored data on the physical medium from the moment that the microcircuit of this medium contains their identifier. Such a solution is described, for example, in document EP-A-1291868. A disadvantage of this solution is that it requires for the readers authorized or qualified to read the data contained in the physical mediums to be known in advance to establish a list thereof.